Stabilizing vanadium containing fuel oils



Patented Mar. 17, 1953 UNITED STATES i TENT OFFICE STABILIZING'VANADIUM. CONTAININ G FUEL OILS No Drawing.

Application December 6, 1949, Se-

rial No. 131,506. In Great Britain October 21,

2 Claims.

The present invention relates to improved'hydrocarbon fuel oils of thetype which contain vanadium compounds, which compounds are liable to bedeposited as solid vanadium pentoxide on combustion.

Heavy residual fuel oils have, for a long time, been used insteam-raising boilers and the like. Combustion systems of this type arecomparatively crude and the deposition of ash from the fuel inside thesystem, while reducing its overall efficiency, is not a problem of majorimportance. More recently residual fuels have been proposed for use inmore sensitively adjusted systems such. as gas turbines and dieselengines, and in systems such as these where the tolerance between movingparts is small and where restriction to gas flow must be avoided, thebuild-up of deposits'is a serious problem.

Residual fuel oils from certain crudes, especially Venezuelan, containsubstantial amounts of vanadium. While some of the ash-formingconstituents are present as solid impurities and may be largely removedby such methods as filtration or centrifuging, it appears that thevanadium is present in oil-soluble form, probably as vanadiumnaphthenates, and accordingly cannot be removed by simple mechanicalmethods;

When such fuels are burnt in boiler furnaces through. atomizing burnersof conventional type, it is found that deposits containing a very largeproportion of vanadium pent'oXide are formed in the system. Thesedeposits are undesirable since they reduce the thermal emciency andprobablyhelp to catalyze the reaction 2SOz+Oz- 2SO3, which is generallyconsidered to be the cause of flu gas corrosion. Nevertheless, thedeposits may be cleaned off periodically without undue difiiculty, andtheir presence does not prevent the furnace from working.

In contrast to this, when. vanadium-containing oils are burnt in gasturbines or diesel engines. the deposits tend to build up on theturbine. blades or round the exhaust valves respectively, and in duecourse this may reduce the eificiency of the engine to an extent whichnecessitates dismantling and cleaning it. Furthermore, with. highvanadium fuels this. necessity may arise-with uneconomic frequency.

In summary, therefore, the. presence of Vanadium compounds in residualfuels is alway disadvantageous and the disadvantages become morepronounced as the degree of precision of the equipment in which they areused increases.

The object of the present invention is to provide an improved fuel inwhich this disadvantage 2 is alleviated or obviated altogether, and theuseof which will tend to remove existing vanadium oxide deposits whenused in equipment in which they have already been formed, andaccordingthereto there is incorporated in the vanadiumcontaining fueloil a minor proportion of an oilsoluble organic halogen compound. Alsoincluded within the scope of the invention is the method of operatingcombustion apparatus in which vanadium-containing fuel oil is burntwhich comprises carrying out the combustion in the presenceof a minorproportion of an oil-soluble organic halogen compound. In this method ofopcrating there may be used the improved fuel already'described, or thevanadium-containing fuel may be used unblended, and the organic halogen.compound, e. g., in the form of a relatively concentrated solution inmineral oil, injected into-thefuel system either before or into thecombustion: chamber, the main thing being to ensure that the halogencompound is present during the actual combustion of the fuel. As amodification of: the process, volatile inorganic compounds such as HClcould be employed in this manner.

The halides and oxyhalides of vanadium are reasonably volatile at thecombustion temperatures involved (QM-1200" F.) and it appears that theyare probably formed in preference to vanadium oxide, provided that thehalogen is present during the combustion. While it is not intended to bebound by the accuracy or otherwise of any theory put forward, it isconsidered that injection of the halogen compound at a later stage ofthe combustion. cycle, or in other. words into the hot exhaust gaseswould be considerably less eflici'ent. Nevertheless, particularly inthecase of furnaces, there maybe no clear out line of demarcationbetween combustion and flue gases, and it is within the scope of thepresent invention to inject the halogen compound into'the gas stream atany point where the temperature is sufficiently high to causesubstantial scavenging of the vanadium. As already indicated, however,it is preferred to have the halogen present inthe fuel beforecombustion.

The amount of halogen compound to. beadded will depend upon the amountof vanadium present and in general should be in excess of the amounttheoretically required. At the sametima. the question of corrosion ofthe turbine or furnaceshould be considered, so that excessive. amountsof, halogen should. not be used. For any normal fuel it will be foundthat an amount of additive equivalent to /2 chlorineby weight willprovide a substantial theoretical excess, and'that quantities of theorder of 0.1% or even less will still provide ample halogen foreifective scavenging. Owing to the low cost of fuel oil, it is desirablethat the amount of additive be kept as low as practicable, and for thesame reason it is preferred to use relatively available highlyhalogenated compounds such as carbon tetrachloride, ethylene dichloride,chloroform and hexachlorethane. Other compounds such as chlorobenzenesmay be used but the aliphatic compounds appear to be more effective.While the use of halogens other than chlorine is theoreticallypracticable, they are undesirable on economic grounds, and theirphysical properties are less wel1 suited to the purpose of the inventionthan are those of the chlorides and oxychlorides.

Preliminary laboratory tests indicated that the reaction of organichalogen compounds, of the type mentioned above, with vanadium pentoxidestarted below red. heat and became more vigorous as the temperature wasincreased to red heat. In order to confirm that this result wasrepresentative of what would occur in practice, a pair of experimentalruns were made on an open-cycle gas turbine. In such a turbine, thecombustion gases pass through the turbine system, in contrast to aclosed cycle turbine in which the operating medium is hot air. When runon gas oil, the unit can be run more or less indefinitely withsatisfactory results.

For test, there was selected a fuel having a high ash content with theash preponderantly vanadium. The fuel, a heavy fuel oil, had thefollowing characteristics:

Specific gravity 0.9634 Redwood viscosity at 100 F secs 966 Ash "percent 0.06 Sulphur do 2.2 Ash analysis:

Vanadium as V205 per cent 81.8 Iron as F8203 do 5.6

Nickel, calcium and sodium not determined In the first run, this fuelwas used without any additive and starting with a clean turbine. Thetest terminated after hours running, with a steady power drop, which,when the test finished had reached (i. e., the final power output,

was of the initial power output).

On openin up the turbine for inspection, it

Deposit on Deposit on 151: and 2nd 3rd and 4th l'OW blades row bladesVanadium as V105 60.1%. Iron as FezOa 5.5%. Nickel as NiO. 4.3%. Calciumas CaO 14.3%. Sodium as NazO 8.3%. Sulphate as SOL. 8.3%. Moisture 4Present.

From this result it will be quite apparent that the presence of thevanadium in the fuel oil has 4 rendered the turbine virtuallyinoperative in as short a period as 30 hours.

The turbine was then cleaned and the test run Was repeated using thesame fuel but with the addition of /2% by weight of carbontetrachloride. This additive has the merits of high chlorine content andready availability, but its boiling point is rather low if the fuel isto undergo prolonged storage.

Using this modified fuel, the turbine ran perfectly normally for hourswith no measurable power drop. Since it Was considered that anypotential adverse effects would have begun to show themselves after 70hours running, and since there was no trace of any such effect, the testwas stopped deliberately after the '70 hours and the turbine opened forinspection.

In comparison with the first test the amount of deposit was extremelysmall and confined to the first row of stator and of rotor blades.Furthermore, What deposits there were on the blades were flaky andloose. No corrosion due to halogen was observed. For comparison with theprevious deposits, analysis of the deposit from the first row of statorblades is given below:

Vanadium as V205 per cent 77.1 Iron as F6203 dO 3.6 Nickel as NiO d0-5.1 Calcium as CaO do 1.7 Sodium as NazO do 2.1 Sulphate as S03 do 8.4Chloride as Cl do 1.1 Moisture Present Owing to the construction of theturbine and the nature of the deposits it was not feasible to conductthe test on quantitative lines and relate the quantity of vanadiumdeposited on the engine in each run to that contained in the fuel burntduring the run. Nevertheless it was obvious to the eye that the amountof deposits in the second run was a, very small fraction of that of thefirst run, despite the fact that over twice as much fuel was burnt. Inaddition, there is the incontrovertible fact that in the first run, theengine was forced to a virtual standstill after only 30 hours running,whereas the second run could apparently have continued indefinitely.

It will be clear from this test that the improved fuel of the presentinvention does most effectively suppress vanadium deposition, and thatequally beneficial results would be experienced when using it in steamboilers or diesel engines. When used for diesel engines,. in particularmarine diesels, it is desirable that'the fuel should also be centrifuged(e. g., treated in a centrifugal purifier and/or clarifier) to removeoil-insoluble matter. Furthermore, when'used for gas turbines orfurnaces it may be desirable to inject liquid water into the systemperiodicallyin order to remove deposits, primarily consisting of sodiumsalts, which may have built up.

What is claimed is:

1. A fuel composition consisting of a vanadiumcontaining heavy fuel oiland 0.5% by weight of an oil-soluble halogen compound chosen from theclass consisting of carbon tetrachloride, ethyl ene dichloride,chloroform and hexachlorethane; 2. Composition according to claim 1 inwhich the halogen compound is carbon tetrachloride.

THOMAS CHARLES GORDON THORYPE. EDWIN MATHIESON DODDS.

(References on following page) 8 7 REFERENCES CITED Number Name Date Thfollown references are of record in the 2,213,281 De Bidder 15, 1940file :i this p at ent: 2,4 1,751 Bro-ggi May 18, 1928 2,460, L 1, 19 9UNITED STATES PATENTS 5 yons Feb Number Name Date FOREIGN PATENTS238,867 Draper Mar, 15, 1881 um r Country Date 1,098,412 Shaw June 2,1914 ,506 Great Britain Apr. 14, 1936 1,637,007 North July 26, 1927 9,692 Great Britain Dec. 5, 1938 2,078,958 Lysholm May 4, 193 10

1. A FUEL COMPOSITION CONSISTING OF A VANDIUMCONTAINING HEAVY FUEL OILAND O.5% BY WEIGHT OF AN OIL-SOLUBLE HALOGEN COMPOUND CHOSEN FROM THECLASS CONSISTING OF CARBON TETRACHLORIDE, ETHYLENE DICHLORIDE,CHLOROFORM AND HEXACHLORETHANE.